The default Java security properties configuration did not restrict access to the com.sun.org.glassfish.external and com.sun.org.glassfish.gmbal packages. An untrusted Java application or applet could use these flaws to bypass Java sandbox restrictions. This update lists those packages as restricted in the java.security file.
Note that the addition of the mentioned packages to the package.access properly list is tracked under CVE-2012-5076 and CVE-2012-5074 (see also bug 865359).